Question

$14.P.022_NegPattern.jpg$

In the region shown in the diagram above there is an electric field due to a point charge located at the center of the magenta circle. The orange arrows indicate the magnitude and direction of the electric field at the locations shown.

What is the sign of the source charge?  ---Select--- zero positive negative not enough information  
Now a particle whose charge is -4e-09 C is placed at location C. Which arrow (a-j) best indicates the direction of the electric force on the -4e-09 C charge?  ---Select--- a b c d e f g h j
$14-068-direction_rosette.jpg$

The electric field at location C has the value < 5000, 5000, 0 > N/C. What is the unit vector in the direction of $$ \vec{E} $$ at this location?

$$ \hat{E} = $$

What is the electric force on the -4e-09 C charge?
$$ \vec{F} = $$

What is the unit vector in the direction of this electric force?
$$ \hat{F} = $$

Two dipoles are oriented as shown in the diagram below. Each dipole consists of two charges +q and -q, held apart by a rod of length s, and the center of each dipole is a distance d from location A. If q = 5 nC, s = 1 mm,and d = 9 cm, what is the electric field at location A?
(i know you use the equation E=k3d/3p
Hint: draw a diagram and show the direction of each dipole's contribution to the electric field on the diagram (you do not have to turn in the diagram).

$14-074-two_dipoles_A.jpg$

okay well ive been struggling to slove these two problems. I need help on solving these problems.

Answer 1

The electric field due to central charge is away from charge. So central charge is positive. The electric force F-qE. The charge q is negative so the force will be antiparallel to the E at location c. So correct option is (b) The direction of the electric field is along the direction of arrow C. The electric field at location C is, E (5000,5000,0) N/C The unit vector in the direction of E is 5000 5000 (5000) (5000) +o (5000) (5000) +0 0.707,0.707,0 The electric force on the charge-4×10-9 C is. 4x10) (5000,5000,0) 2(-2×10-5 ,-2×10-5 . ON The unit vector of electric force is, 2x10-3 -2x10-5 2x10) (2x10+2x10") (-2x10)+ 2x10%) +(-2×10%) +0 0.707,-0.707,0